I installed 11.5.1 on one of my older iMacs today (11,1 Late 2009 27", 2.66 i5, Radeon HD 4850 512Mb). As expected, very slow until the boot volume was patched, then it took off. Performance is very good considering the age of this puppy. I ran SilentKnight to see if it needed any further upgrades and noticed that SIP and SSV are disabled. Is this normal for this late 2009 iMac/OCLP? The key to getting this late 2009 27" working on Big Sur, was installing OCLP onto an external SSD. (2.5 Crucial 64Gb SSD/3.0 USB). Every USB flash drive or microSD I tried failed. You OCLP guys are nailing these things! My hat is off to you, thanks!